Mortality of first world war military personnel: comparison of two military cohorts.

Objective: To identify the impact of the first world war on the lifespan of participating military personnel (including in veterans who survived the war).

Design: Comparison of two cohorts of military personnel, followed to death.

Setting: Military personnel leaving New Zealand to participate in the first world war.

Participants: From a dataset of the New Zealand Expeditionary Forces, we randomly selected participants who embarked on troopships in 1914 and a comparison non-combat cohort who departed on troopships in late 1918 (350 in each group).

Main Outcome Measures: Lifespan based on dates of birth and death from a range of sources (such as individual military files and an official database of birth and death records).

Results: A quarter of the 1914 cohort died during the war, with deaths from injury predominating (94%) over deaths from disease (6%). This cohort had a significantly shorter lifespan than the late 1918 "non-combat" cohort, with median ages of death being 65.9 versus 74.2, respectively (a difference of 8.3 years shown also in Kaplan-Meier survival curves, log rank P<0.001). The difference for the lifespan of veterans in the postwar period was more modest, with median ages of death being 72.6 versus 74.3, respectively (a difference of 1.7 years, log rank P=0.043). There was no evidence for differences between the cohorts in terms of occupational class, based on occupation at enlistment.

Conclusions: Military personnel going to the first world war in 1914 from New Zealand lost around eight years of life (relative to a comparable military cohort). In the postwar period they continued to have an increased risk of premature death.